Catalytic conversion of hydrocarbons



Feb. 23, 1943. A. BELcHx-:Tz

CATALYTIC CONVERSION OF HYDROCARBONS Original Filed June 29, 1940Patented Feb. 23, 1943 CATALYTIC CONVERSION OF HYDROCARBON S ArnoldBelchetz, Kew Gardens, N. Y., assignor to The M. W. Kellogg Company,Jersey City, N. J., a corporation of Delaware Original application .lune29, 1940, Serial No. 343,222. Divided and this application June 28,1941, Serial No. 400,253

2 Claims.

The present application'is a divisional application of my co-pendingapplication, Serial No. 343,222, filed June 29`, 1940, the latterapplication being a continuaticn-in-part application of my co-pendingapplication, Serial No. 274,670, filed May 20, 1939, now U. S.' Patent2,253,486.

The present Ainvention relates to the catalytic conversion ofhydrocarbons into lighter hydrocarbons of lower-boiling point orhydrocarbons otherwise altered in structure. More particularly, myinvention relates to the catalytic conversion or cracking ofhigh-boiling petroleum oils to low-boiling products, and the catalyticreforming of petroleum oil fractions such as naphtha and gasoline.`

The catalytic conversion of hydrocarbons involves, in general, twostages, a conversion stage wherein the hydrocarbons undergoing treatmentare contacted with the catalyst under conditions adapted to effect thedesired conversion, and a regeneration stage wherein the carbonaceousdeposit formed on the catalyst during the conversion stage iseliminated. In its preferred aspect, my invention contemplatesparticularly an improved process involving a conversion stage whereinthe hydrocarbons undergoing treatment are passed through the conversionzone in the form of vapor having the catalyst in finely dividedcondition suspended therein; and a regeneration step wherein usedcatalyst, after separation from the gaseous conversion products, issuspended in oxygen-containing gas and carried thereby through theregeneration zone to regenerate it by burning off deposited carbonaceousmaterial.

This method of catalytically converting hydrocarbons has certainadvantages arising particularly out of the relative intimacy of contactwhich it affords between the suspended catalyst and the carrier gas bothin the conversion and regeneration operations. It exhibits, however,various disadvantages the elimination of which is one of the primaryobjects of my invention.

One of the objects of this invention is the provision of a procedure forheating and vaporizing the hydrocarbon preparatory to its passage to theconversion zone under such conditions as to avoid undesired thermaldecomposition effects and the accomplishment of this result by thedirect utilization of the heat of regeneration.

thereof on the catalyst. Various other objects and advantages of myinvention will be' evident to those skilled in the art as thedescription thereof proceeds.

One of the features described and claimed in said co-pendingapplication, Serial No. 274,670 now U. S. Patent 2,253,486, resides inthe charging of the catalyst and hydrocarbon feed to the conversion zonein proportions which are markedly different and advantageous comparedwith those indicated by conventional practice. In such practice, thisratio is determined primarily on the basis of the activity of thecatalyst and the extent to which deactivation thereof occurs during theconversion stage, the objective being,

` in general, tolimit the quantity of catalyst em- Another object of theinvention is the propioyed to the smallest feasible amount consistentwith the production of the desired extent of conversion, both because ofthecost of the catalyst and processing costs incidentto its circulation.Limiting factors with respect to the proportion of the catalyst thusemployed relative to the hydrocarbon charged, are the total carbonaceousmaterial deposited during the conversion of a given amount of feed tothe desired extent, and the quantity of carbonaceous depositwhich thecatalyst is capable of carrying before its activity drops to a pointWhere its continued use is not feasible or desirable.

One feature of this invention involves the mixture of the liquidhydrocarbon feed with preheated catalyst, preferably at a temperaturesufflcient to vaporize the feed, the necessary preheating of thecatalyst preferably being effected in the regeneration reaction.

Another feature of this invention involves the controlled combustion ofthe used catalyst in such manner that a predetermined quantity ofcarbonaceous material is left thereon.

The various features of this invention are interrelated in such mannerthat their conjoint use is desirable. However, various features thereofare susceptible of application independently of the others, as Iwill beapparent to those skilled in the art.

The foregoing and various other features of the invention will beapparent from the following description thereof, given with reference tothe appended drawing which illustrates diagrammatically suitableapparatus for its practice.

The drawing is a diagrammatic illustration of suitable form of apparatusfor the practice of the embodiment of the invention involvingthe featureof the use of preheated catalyst to vaporize the feed stock.

Referring to the drawing. the feed to the system, for example, a reducedpetroleum crude, enters from any convenient source indicated by thenumeral I and is pumped by pump 2- to a heater or furnace 8 wherein-itis preheated I-to a suitable temperature and then flash evaporated inevap-v" cumulator 8 through line I8. The gas oil con-v densate is pumpedby pump IIl through line I8 to heat exchanger 8 and into line I2. Partof the gas oil is returned as reflux to the evaporator through line I4.

The apparatus described above is merely illustrative of conventionalapparatus forsupplying the gas oil or other treated hydrocarbon at asuitable temperature for the following conversion operation.

'I'he preheated fresh feed in transfer line I2 may be advantageouslycombined with a hot recycle oil introduced through line I4, the combinedstreams passing to the conversion stage through line I5. The oil passesthrough line I5 into pipe I 8 constituting an extension of theconversion reactor I1. Hot preheated catalyst is supplied from drum I8by helical feeder I8 and mixed with the oil in pipe I8. Line 88indicates the upper level of the catalyst collected in drum I8. Thetemperature of the catalyst and quantity of catalyst used are such as tocause vaporization of the oil thereby forming a suspension of thecatalyst in the vapors. Sufficient steam or other suitable gas toinitially disperse the catalyst as discharged from feeder I9 ispreferably introduced through -line 20. Steam or other suitable gas maybe supplied in greater quantities through line 28 when required tosupplement the vapors resulting from the vaporization of the feed stockto produce the required volume of gas to carry the catalyst through theconversion reactor Il. The ratio by weight of the catalyst to fresh feedstock is preferably maintained and regulated as set forth in detailhereinafter. The gaseous mixture of feed stock, catalyst and steam flowsupwardly through reactor II during which flow conversion or cracking ofthe oil to the desired extent occurs.

Reaction products pass from the top of reactor I1 to a suitableseparator system to separate the catalyst from the vaporous reactionproducts. That shown comprises a settling tank 2I in which the majorproportion of the suspended catalyst is separated, the separatedcatalyst flowing by gravity from the bottom of tank 2I through conduit22 to the top of a steam stripper tower 28 and the vapors containing arelatively small fraction of fine catalytic material are withdrawn atthe top through line 24. These vapors pass through line 24 to a suitableseparator such as a cyclone type of dust collector 25 wherein most ofthe remaining suspended catalyst is separated and then passed to tower28 by gravity flow from the bottom of the separator through line 28.Tower 28serves to displace hydrocarbon vapors contained in the voidsbetween theparticles of catalyst and is suitably provided with bailies2lV to eectively expose the catalyst passing downwardly therethrough -tothe displacing action of.v 75,

used catalyst, is Passed through line 8| to a suitable type offractionator 82 wherein a low-boiling fraction such as gasoline andfixed gases may be separated from the high-boiling products such aslight and heavy cycle gas oils. Infractionator 82 the rconversionproducts may, for example, be fractionated into a low-boiling fractionincluding gasoline and ilxed gases withdrawn as the overhead productfrom the fractionator through line 88, an intermediate product such aslight gasoil withdrawn as a side cut through line 84, and a residualhigh-boiling fraction such as heavy recycle gas oil withdrawn throughline 85, cooled in cooling coil 8|, and pumped to storage through line88.V i

In the bottom of fractionator 82 suitable means may be provided forseparating residual catalyst present in the vapors introduced throughline 8|. Asshown, these means comprise a line 8lv through which aportion of the high-boiling frac- A tion withdrawn through line 85 isreturned to the fractlonator over bames 88 which deflect the vapors fromline 8l into intimate contact with the returned fraction whichconsequently adsorbs or scrubs out residual catalyst present in thevapor. After passing over baiiles 88 the scrubbing liquid collects inthe bottom of fractionator 82 from whichit is withdrawn through line 88and pumped by pump 48 into line I4 for utilization as a re-u cycle oil,vas previously described.

Used catalyst is fed from drum 88 by screw feeder 4I to pipe 42 andcarried therein by a current of oxygen-containing gas such as airinjected through line 48 to regeneration or combustion chamber 44wherein combustion of the carbonaceous deposit on the spent catalystoccurs during the passage of the catalyst therethrough. Steam may beintroduced when desired through line 45. Line 82 indicates the upperlevel of the catalyst in drum `88. 'I'he proportion of oxygencontaininggas injected relative to the quantity of used catalyst is preferablymaintained and resulated, as described hereinafter in detail.

Combustion gases bearing the regenerated catalyst pass from chamber 44into a suitable recovery system for separating the catalyst. As'

shown, this system comprises a settling tank 48 wherein most ofthecatalyst is' separated and flows downwardly therefrom through conduit 41l to surge drum I8. The separated gases containing a small residualamount of catalyst ilnes leave separator 48 at the top through line 48and pass to a cyclone type of dust collector 48, wherein substantiallycomplete separation of the catalyst is eifected. The separated catalystfrom collector 48 then flows downwardly through line 58 and is combinedwith the initially separated catalyst'in drum 'I8 from which it is fedto the conversion stage by feeder I8, as previously de-4 m, scribed.Drum I8 and feeder I8 may be suitably provided with heat insulationmaterial to obviate loss of heat by the regenerated catalyst in itspassage therethrough.

The range of catalyst-to-on-reed ratio suitably' and preferably employedland other preferred:

The gaseous suspension withdrawn from septhe folprocessing conditions,is illustrated by lowing examples.

In one example, a petroleum gas oil having a gravity of 31.4 A. P. I.was used as the feed stock to be catalytically converted or cracked bythe process to a low-boiling stock having a required amount ofhydrocarbon within the gasoline boiling range. This particular gas oilwas produced by the flash evaporation of a reduced crude and constitutedthe volatile portion thereof amounting to about 901% of the crudecharged to the evaporator. In the process of converting this particularoil to the desired extent. it was determined that coke or carbonaceousmaterial appearing as a deposit on the catalyst would be produced to theextent of 3.5% by weight of the charged gas oil. A temperature of 865 F.was chosen as representing a suitable mean temperature for the reactionwhich, since the conversion reaction is endothermic, corresponded to aninlet temperature to the reactor of about 880 F., and an outlettemperature of 850 F. The deactivationu temperature of the particularcatalyst employed was ascertained to be approximately 1000 F., thistemperature being the maximum temperature to which the catalyst could besafely subjected under the regeneration conditions without undueimpairment of its catalytic ac- Vcatalyst in sufiicient amount to absorba definite minimum amount of the heat of regeneration, this ratio Rbeing determinable by the application of a generalized formula derivedby the application of the principles of my invention, as follows:

CH K

Rian-T2) In this formula, R represents the catalyst-to-oil weight ratio;the vsymbol C, the fraction of the gas oil or other hydrocarbon charged,converted to coke or oarbonaceous material and deposited on the catalystduring the conversion; H, the heat of combustion of the coke orcarbonaceous material expressed in B. t. u.s per lb.; S, the specificheat of the. catalyst; T1, the deactivation temperature in degreesFahrenheit of the catalyst; T2, the temperature in degrees Fahrenheit ofthe catalyst on entering the regeneration zone; and K, a fractionalcoeiilcient having a lower limit determined by the extent to whichexpedients other than the heat absorption capacity of the catalyst maybe employed to dissipate the heat of regeneration.

In this particular example, the regeneration was effected in accordancewith the preferred mode of practising my invention wherein thev 0.035;16,400; 0.22; and 1000. Since the used catalyst may be advantageouslytransferred directly from the conversion zone to the regeneration zonewithout substantial intermediate cooling in accordance with myinvention, which procedure was followed in this instance, the value ofT2 corresponded approximately to the outlet temperature of theconversion zone, namely, 850. Accordingly, substituting these values forthe corresponding symbols in the above formula it is evident that themaintained catalyst-to-oil weight ratio, R, is equivalent to the ratio,

By the maintenance ofthe catalyst-to-oil ratio at the relatively highvalue of 14.5, as determined above, the absorption of the heat ofregeneration at a temperature below the deactivation temperature of thecatalyst, was readily and effectively accomplished solely through themedium of the heat absorption capacity of the catalyst and thecombustion gases without the use of extraneous cooling means.

It is to be noted that the ratio as above determined, is not sharplycritical and may be increased or decreased. these variations in generalcorresponding to permissible variations in the numerical limits of thecoeillcient K. In the above specific example, for instance, thecatalystto-oil ratio may be maintained at a larger figure than 14.5,thereby assuring the circulation of a quantity of catalyst not onlysufficient but in excess of that needed for the desired minimumabsorption of heat by the catalyst during the regeneration reaction. Theamount of such surplus catalyst will normally be controlled by economicconsiderations dependent upon the cost of the surplus catalyst and theprocessing expense incident to its circulation. Since these factors willnormally outweigh any advantage to be gained by the circulation ofsurplus catalyst, it is contemplated that the practice of my inventionwill usually and preferably be practised with an oil-to-catalyst ratiowherein K has a value not very greatly in excess of that employed in theabove example.

The oil-to-catalyst ratio, as above determined, may also be decreased tosome extent, such changes corresponding to the lower limiting value ofthe coefficient K. For example, thev use of a lower ratio andcorresponding lower K value may be feasible through the use to alimitedr extent of cooling coils or similar extraneous cooling means inthe regeneration zone. It is contemplated, however, that in the practiceof my invention in its preferred aspect wherein the heat of regenerationis largely absorbed by the catalyst that the value of K, will be greaterthan 0.2 and preferably greater than 0.5.

In the conversion of the gas oil used in the above example, theprocedure followed was that previously described in connection with theappended drawing, the catalyst-to-oil ratio being maintained at aminimum of 14.5 to 1, as above determined, and air being introducedthrough line 43 in quantity suiiicient to supply only the theoreticallyrequired amount of oxygen to burn oil or reduce the concentration of thecarbonaceous deposit to the desired extent; also the hot regeneratedcatalyst was' withdrawn from drum I8 and thereafter mixed with the feedstock Without any substantial intervening cooling, and

.. contained sufiioient heat to vaporize the feed stock introduced at atemperature of about 550 with a minimum amount of carbonaceous materialthereon mounting to 1.5% by weight of the catalyst. In passing throughthe conversion zone the carbonaceous material concentration on thecatalyst under the conditions of this particular example increased to1.74% and accordingly, in the regeneration stage, the carbonconcentration of the catalyst was reduced from 1.74% to 1.5%.

'I'he average velocity of the vapors through the reactor may be of theorder of about 10 feet per second and the vapor contact time of theorder of about 6 seconds; such conditions correspond to an averagecatalyst concentration in therel actor of about 6 pounds per cubic foot.

The maintenance of a definite minimum concentration of carbonaceousmaterial on the catalyst as exemplified by the above example, has

important and distinctive advantages. It assists in the regenerationreaction since the rate of combustion is accelerated and more readilycontrolled by the presence of an amount of carbonaceous material inexcess of that which is to be removed by combustion. The retention of,residual carbonaceous material also makes it possible to discharge theregeneration combustion gas with a relatively low percentage or in somecases, entirely free of oxygen, and the gas is thus better adapted foruse for various purposes. Also, in certain'instances, particularly incatalytic cracking in the presence of alumina-silica type of crackingcatalyst such as Super-Filtrol, the conversion reaction is faciiltatedby the presence of a small amount of residual carbon and in mostinstances the advantages obtained in regeneration by the maintenance ofa residual carbon concentration will outweigh the disadvantages, if any,resulting in the conversion stage. The residual carbon concentrationmaintained may depart-somewhat from the value of 1.5% regarded as theapproximate optimum in the foregoing example wherein a Super-Filtroltype of alumina-silica cracking catalyst was ernployed.' Preferably,this permissible range is confined to about 0.5% to 2.0%, by weight ofthe catalyst, ror the narrower range of about 0.8% to 1.5%.

A number of highly advantageous results are secured by mixing the liquidfeed stock with the regenerated catalyst while the latter retains theheat imparted to it in the regeneration reaction.

Conventional methods for vaporizing and preheating the oil to therequired conversion temperature would frequently result in substantialthermal decomposition or crackingf which is undesirable because of thelow quality of products thus obtained, particularly with respe'ct tooctane number and ultimate amount of coke formed, compared with thoseproduced b'y complete catalytic conversion. Due to the intimate contactbetween the hot catalyst and feed stock and resultant rapid and emcientvapcrization, undesired thermal cracking" is largely obviated.Substantial savings are further secured by the resulting direct use ofthe major proportion of heat evolved during the regeneration stage.

Any type of catalyst suitable for effecting the desired conversion maybe employed in the pract-ice of rnv invention. For the conversion orcracking of high-boiling fractions such as gas oil to low-boilingfractions such as gasoline, I regard cracking catalysts of thealumina-silica type as especially suitable, this term lbeing inclusiveof cracking catalysts such as certain types of activated clays orsynthetically produced mixtures or compounds of alumina and silica. Thecirculated catalyst may be composed entirely of the active catalyticmaterial and is preferably pre dominantly composed thereof. However, theactive catalyst material may be associated with supports, extenders orsolid diluents which for the purpose of my invention are to beconsidered as part of the catalyst, since such solid diluents. etc.,will function in a manner similar to the active part of the catalystrelative to the absorption of heat in the regeneration zone and thetransfer of this heat to the hydrocarbons undergoing treatment. Whenalumina-silica type of cracking catalysts are employed, the practice oi'my invention will* usually involve catalyst-to-oil weight ratios greaterthan 2.5 to 1, and preferably greater than 5.0 to 1.

From the foregoing it will be apparent that the process thereindescribed accomplishes the objects of my invention, and that variousfeatures thereof may be utilized to advantage either conjointly orseparately. It will further be readily apparent to those skilled in theart that while the invention has been illustrated and described withrespect to a preferred operation and examples, and with references tosuitableapparatus for its practice, the invention is not limited to suchexempliiications but may variously be practised and embodied within thescope of the claims hereafter made.

I claim: i

1. In a process for the catalytic conversion of high-boilinghydrocarbons into low-boiling hydro carbons within the gasoline boilingrange involving passing a stream of the high-boiling hydrocarbons havinga solid, incombustible cracking catalyst suspended therein through aconversion zone for a time and at a temperature adapted to eilect therequired degree of conversion to lowboiling hydrocarbons and alsoresulting in acarbonaceous deposit on the catalyst, separating the usedcatalyst from the vaporous conversion products, suspending the Iusedcatalyst in an oxygencontaining gas and passing the suspension through aregeneration zone to burn oi! carbonaceous material deposited on thecatalyst,- and returning the catalyst for reuse in the conversionreaction, the improvement which consists in introducing the usedcatalyst into the regeneration zone and burning oil. the carbonaceousmaterial in said zone under such conditions as to leave a residualquantity of carbonaceous material on the catalyst amounting to about0.5% to 2.0% of the weight of the regenerated catalyst as dischargedfrom said regeneration zone and reused in the conversion zone,withdrawing the regenerated catalyst from said regeneration zone andadmixing it with liquid hydrocarbon feed. stock while retainingsuiilcient heat to vaporize the feed stock, and returning said catalystin suspension in the vapors thus produced to said conversion zone.

2. A process for the catalytic conversion of tion products andregenerating it by passage 10 through a regeneration zone, whilesuspended in an oxygen-containing gas, withdrawing the regeneratedcatalyst frorn said regeneration zone and admixing it with liquidhydrocarbon feed stock while retaining sufcient heat to vaporize thefeed stock, and returning said catalyst'in suspension in the vapors thusproduced to said conversion zone.

ARNOLD BELCHE'IZ.

